Virtual design and construction of transportation projects

The use of intelligent computer models and processes such as Building Information Modeling (BIM) and Civil Integrated Management (CIM) is transforming the delivery of transportation programs. (CIM is a term now being promoted by the Federal Highway Administration under the Every Day Counts initiative.) Owners, designers, and contractors are using these processes to design, build, and simulate projects virtually before executing them in reality. The use of virtual modeling increases communication and coordination among project stakeholders by providing an easily accessible vision of the entire project. 3D and 4D models (where time is the 4th dimension) reduce risks, errors, and inefficiencies that are common to more traditional forms of project management.

Parsons Brinckerhoff – a global consulting firm assisting its clients on the planning, development, design, construction, operation, and maintenance of critical infrastructure – has been using these innovative processes for many years to gain efficiencies on large municipal transportation projects. Recent projects include the San Francisco-Oakland Bay Bridge, San Francisco’s Presidio Parkway, and Seattle’s Alaskan Way Viaduct.

I-95 New Haven Harbor CrossingWith the support and foresight of the Connecticut Department of Transportation (CTDOT), Parsons Brinckerhoff is utilizing 3D/4D modeling on the I-95 New Haven Harbor Crossing Corridor Improvement Program, a multimodal transportation project that features public transit enhancements and roadway improvements along 7.2 miles of I-95 in New Haven, Conn. This stretch of roadway runs through a densely developed urban area and is part of the heavily traveled Northeast Corridor between New York and Boston.

Constructed in the late 1950s, the highway and bridges in this area accommodate traffic volumes in excess of 140,000 vehicles per day, more than three times the amount for which they were designed. The project includes capacity improvements as well as replacement of the existing Pearl Harbor Memorial Bridge, known locally as the Q-Bridge ("Q" for Quinnipiac River). The new Q-Bridge will accommodate 10 lanes of traffic and is the first extradosed cable-stayed bridge in the country.

CTDOT began studying remedies for the area’s traffic congestion in 1989. Construction began in 2000 and is more than 60 percent complete as of spring 2013. The entire project is expected to be finished in 2016. Parsons Brinckerhoff is CTDOT’s program manager on this project, coordinating 28 construction contracts for various portions of the program. To support this effort, the firm is using both 3D and 4D project models for construction planning, project collaboration, and program communication.

Construction challenges"Three highways converge as you approach the Q-Bridge on the west side and the project has numerous ramps and access roads that feed into this complicated interchange," said Joe D’Agostino, Parsons Brinckerhoff’s deputy project manager on this project. "But during the reconstruction of the bridge and interchange, traffic has to be maintained."

Several temporary ramps will accommodate traffic during construction of the permanent roadways and structures. Throughout the project, traffic is being shifted between these temporary or finished sections; any closures or shifts on I-95 and associated ramps must be limited to very small windows and must occur on very specific and inflexible dates. As a result, the overall project schedule and all the various construction activities are driven by these traffic shifts. The Q-Bridge itself also is being built in sections, with traffic detoured to a new span followed by demolition of the original existing span. Therefore, a large part of the ongoing public outreach program is the communication of the timing and details of these traffic shifts. This has been a highly successful aspect of the project.

The sheer complexity of this project’s scope is one challenge; the large number of interrelated construction activities is another. "The physical area of the contracts sometimes overlap at transition points – at the western approach to the Q-Bridge for example – and the contractors must work in very close proximity to each other," D’Agostino said. "Space is very tight already because the new ramps and roads are being built in-between existing structures." These tight quarters require careful and precise construction logistics, planning, and sequencing.

Virtual constructionTo support construction planning and management, Parsons Brinckerhoff developed 3D and 4D models using several BIM software solutions, including AutoCAD Civil 3D, Autodesk 3DS Max Design, and Autodesk Navisworks Manage. The team uses these models for technical analysis, project communication, visualization of construction sequences, and illustrations for the public’s better understanding of the project. Renderings and animations produced from 3D models show stakeholders the ultimate plan and vision for the completed project.

A 3D rendering shows the complex bridge-erection sequence.

The 4D model pairs project design elements with construction activities to virtually display the progression of construction over time. "Originally we developed the 4D model as a visual aid for contractors bidding on the project, using very high-level schedule activities to illustrate basic construction sequencing," recalled D’Agostino. "But now that we’re in the thick of construction, we’ve been adding more detailed elements and construction activities."

These "construction-worthy" models validate and illustrate the many traffic shifts, detours, and associated road closures that constitute the construction process, and support the planning and communication of proposed construction activities and equipment logistics.

Creating the 3D modelsTo simulate accurately the construction process, including demolition of existing structures, the team needed to model proposed project elements – permanent and temporary roadways, ramps, and bridges – as well as the existing infrastructure. For the existing conditions the team imported survey data, digital terrain models, 3D as-built design data such as roadway centerlines, GIS data, and conventional 2D drawings into Civil 3D to combine and rebuild the data in 3D. The Civil 3D model was then moved to 3DS Max Design, a software solution specifically for 3D modeling and photo-real rendering and animation.

Using 3DS Max Design, Parsons Brinckerhoff enhanced the model by adding details such as signs, vehicles, landscaping, and realistic materials. In addition, geospatial data such as aerial imagery and building footprints were imported and optimized in 3DS Max Design to provide surrounding context.

Next, the team created 3D design models of the project. Drawing on a variety of sources again, the team imported 2D and 3D data, including contour data of interim and final surfaces, into Civil 3D to create the 3D model and clean up and reconcile the data sources. The model was moved to 3DS Max Design for additional modeling efforts, surface editing, and addition of materials and finishes.

These models are the basis for the hundreds of still images and animation simulations posted on CTDOT’s project website (www.i95newhaven.com). These high-end project visualizations help the public, the client, and other project stakeholders easily grasp the details of this complicated construction program as well as the day-to-day traffic and detour changes.

Adding the 4th dimensionFor 4D modeling, the team moved the 3D models to Navisworks Manage. More than 2,000 individual activities in the two primary contractors’ schedules are linked to individual elements in the Navisworks model for construction planning and simulation. As construction progresses, the 4D model is used by the extended project team to help visualize and better understand the complexities of the design and the construction process.

A 3D LiDAR point cloud is viewed inside the project 3D/4D model.

"Some of the major contractors on the project are separately using Navisworks, or other 3D modeling systems, to evaluate equipment locations and clearances, and convey their means and methods," D’Agostino said. "In those situations, we incorporate their models into ours, resulting in a shared 3D/4D resource that benefits everyone by improving communication between contractors and program managers."

Latest developmentsCTDOT and the project team continue to innovate on this project and have begun using point cloud management tools such as Autodesk ReCap and Civil 3D to create 3D models from laser scans. For example, one area of the project is particularly tight, where three levels of existing highway ramps (that will eventually be demolished) are just a few feet away from an historic building.

"To plan the demolition, we need to accurately model the ramps and the building," D’Agostino said. "So we incorporated point cloud data captured by the contractors, and are now extracting model elements accurate to within inches."

The I-95 New Haven Harbor Crossing Corridor Improvement Program is on schedule for completion in 2016. To date, Parsons Brinckerhoff has produced more than 200 still and graphic images and more than five hours of animation files for the project. 3D and 4D models have allowed the team to build the project virtually, enabling them to check staging/construction sequences and schedule logic much earlier in the process, better manage site logistics, and more closely synchronize multiple activities.

"Using these tools and processes to increase communication and coordination among all project stakeholders has greatly increased the level of confidence in the design, the schedule, and the overall execution of the program," D’Agostino said. "The end result is reduced project risk, rework, cost, and schedule."

For transportation departments, working with consultants to design and deliver projects using tools and processes such as BIM and CIM is definitely where the transportation industry is headed. The I-95 Corridor Improvement Project represents a great first step by CTDOT in that direction.

Kevin Gilson is director of visualization for the Project Visualization Group of Parsons Brinckerhoff in Denver. Brian Mercure is the assistant district engineer for District 3A – Construction, Connecticut Department of Transportation.